Variable-speed drive for exhaust fans



April 24, 1928.

F. G. SARGENT VARIABLE SPEED DRIVE FOR EXHAUST mus Filed Aug. l8. 1926 Patented A r. 24, 1928.

UNITED STAT S PATENT 'IOFFICE.

rnnnnnrciz e. SARGENT, or wns'rronn, MASSACHUSETTS, AssIenon To o. G. B-

? GENTS SONS oonronATIoN, TION or MASSACHUSETTS.

on GRANITEVILLE, MASSACHUSETTS, A oonrona- VARIABLE-SPEED nnrvn ron EXHAUST FANS.

Application filed August 18, 1926. Serial No. 130,057.

The principal objects of the invention are to provide means for driving the exhaust fan in such a way as to avoid'the drax'ving out of dry air and to so regulate it that the air when it is heavily charged with moisture will be withdrawn, and thus avoid thedraW- ing outessary. In this way the machine can be run so that theright proportion of the damp air or moisture can be removed to give the best results in drying without undue complication of the mechanism.

Other objects and advantages of the invention will appear hereinafter. v f

Reference is to be had to the accompanying drawings in which Fig. 1 is an end tion applied thereto;

Fig. 2'is a side View of that end of the machine; and

Fig. 3 is a detail view similar to Fig. 1

form. I

be applied to various I have shown it showlng a modified The invention can types of drying machines. as applied ber 10 is provided with an endless apron 11 driven by two drums 12 for carrying the material through the drying machine on its upper strand. chine by a fan 13 and circulatesthrough it so as to be drawn out by an exhaust fan 14:

cates a belt shipper or guide 24. In the present form, this operates a belt 25 which is located on a pair of cone pulleys 26 and 27 arranged in opposite positions so that the speed of transmission will vary in accordance'with the position of the belt. Obviously the speed of rotation will be increased or decreased in accordance with the position of this belt on the pulleys, 'This results in rotating the exhaust fan 14 at higher or lower of the moisture when that is not nec-v view of a drying machine. with a preferred embodiment of this 1nven-,

to one in Which the drying cham- The air is driven into the maspeed as the shaft 18 turns. Therefore durmg each revolution 'of haust fan 14: will be driven for a while-at ing in speed,'in this form of the invention. The circulating fan 13 1s dr ven by power the shaft 18, the 6X' maximum speed and then gradually go down to minimum speed and will continue vary' and is connected by belt and pulleys to the shaft 30 of the cone pulley '27 so that both fans will always rotate at thesame time I but not always at the same speed.

more air than is necessary and irrespective Ihave found that the exhaust fan ordi- 'narlly takes out ofthe drying compartment of whether it is too moist or not. This invention cuts down the amount of air it takes out and allows the air to be exhausted until it is comparatively dry and then collect more moisture and be driven out at a higher speed. The exhaust fan is driven ata variable number ofrevolutions per minute so as to take out of the machine the right proportion of the damp 0r moist air to give the best results in drying; It will beunderstood that the cam 20 is designed for the purpose of v securing this particular result.

In theform shown in'Fig. 3, the conical' pulleys above described-are replaced by tight and loose pulleys 36 and 37 and a belt 35 which belt is. operated by the cam 20, the yoke 21, shaft 22 and belt guide 24 as in In this form of theinvention, the exhaust fan, instead of operating all the time at varying speeds, stops and starts automatically. It is timed so that it will start automatically and run until the humidity is taken out of the. drying compartment. Then the fan automatically stops until the air again becomes loaded with sufficient moisture to be taken out. Then the other case.

the fan starts up again and removes the moist air; The time between the starting and stopping of the fan is determined by the amount of moisture which accumulates in the machine. The cam 20 is designed to have the above-mentioned effect, the'design' being controlled by experiment. It will be understood of course that I do not depend upon a cam for this purpose but any equivalent such as an electric time switch or the like can be employed. f I I I Although I have illustrated and described only two forms of the invention I am aware of the fact that other modifications can be made therein by any person skilled in the art Without departing from the scope of the invention as expressed in the claims. There fore, I do not Wish to be limited to all the details of construction herein shown and described, but

What I do claim is:-

1. The combination With a drying machine and its exhaust fan for taking the air out of the drying compartment, of means for moving the material to be dried through the machine, and means connected with the last named means :for controlling the stopping and starting of the fan to cause the fan to take out of the drying coi'i'lpartinents the right proportion of moist air.

2. The combination with a drying machine and its exhaust fan, of an endless apron for conveying the material in the machine and subjecting it to the action of the air therein for drying it, of a shaft rotatable in synchronism with the endless conveyor,

a cam on said shaft, a yoke operated by the cam a sliding guide movable With the yoke as the cam operates, and speed varying pulleys over Which a belt travels connected for operating the exhaust fan, said guide being arranged to shift the belt back and forth, whereby the cam Will control the action of the fan. I

3. In a drying machine, the combination with a drying chamber and means therein for moving the goods to be dried, of an exhaust fan for drying the air out of said goods, two pairs of tight and loose pulleys for driving said fan, a belt shipper for starttrolled by the operating means for shifting the belt shipper to automatically start and stop the fan. 7

I In testimony whereof I have hereunto atfixed my signature.

FREDERICK e. SARGENT.

111g and stopping the fan, and means con 

